The source said: “The chapel holds 225 people and there are lots of marquees being set up in the grounds for the reception so the wedding could have easily been relayed”.

The Royal Family are paying for the wedding inside Windsor Castle and the reception but the taxpayer has been left to pick up the bill for policing the wedding day operation.

The decision of Princess Eugenie to go for a carriage ride through the streets of Windsor after the wedding gave Thames Valley Police a major security operation headache.

Weeks of planning have gone into keeping the royal couple and the public safe and all drains on the route have to be searched and armed and plainclothes officers brought in.

Snipers will be on roofs and the force helicopter will be overhead watching for threats.

Her decision to also invited 1,200 "commoners" to the wedding and to stand outside St George's Chapel but inside Windsor Castle also helped rack up the police bill.

They will all have to be vetted and security searched before entrance is allowed.

It was also claimed yesterday that Princess Eugenie and husband-to-be Jack Brooksbank were having difficulty trying to find 1,200 people to actually turn up for the wedding.

On top of the 850 guests she has invited to be inside St George’s Chapel – compared to 600 that Prince Harry invited – she has invited 1,200 people to watch from outside.

But a Windsor resident claimed on a local Facebook page that wedding planners were so desperate for guests they were inviting people who had car park passes at a royal gardens.

Carolyn Osgood said: “You could they were scraping the barrel when they started sending out invites to people whose only connection was that they have a car park pass for Savill Gardens. True story. You couldn’t make that up.”

Savill Gardens is part of Windsor Great Park and was created by Sir Eric Savill in the 1930s and is operated by the Crown Estate and a car park pass costs £70 a year for entry.

Deborah Poole said on the same Facebook page: “She is a minor royal yet because she is a member of royal family she wants to marry in St George’s Chapel and have a certain level of pomp like her cousin.

“I guess she is entitled to it and it is her special day. We all want a lovely wedding day. But I can’t help but feel she’s being a bit of a hanger on” she said on Windsor Past & Present 2.0

The Queen has agreed to a drone ban being implemented by the Civil Aviation Authority over the grounds of Windsor Castle and the Windsor Castle Estate for the royal wedding.

It forbids the use of unmanned aerial vehicles which can both take photos and video being flown on both the wedding day and the following day when guests leave Royal Lodge.

A Thames Valley Police spokesman said: “A Restriction of Flying Regulation has been granted and this will be enforced and any offenders with drones will be prosecuted”.

They are calling for local residents to be their “drone rangers” and report drone pilots.

The spokesman said: ”Please call us immediately if you see a drone being flown”.

Police not only fear that drones could information to terrorists but that they could run out of power and drop out of the sky and injure the royal couple or well wishers on the route.

They could also put police helicopters watching from above at risk of a collision.